A new study argues that vaccinating boys against HPV isn't the best use of resources, since vaccinating more girls will actually lead to a greater reduction in overall infections. However, there are also political implications to consider.

Back in October, I wrote that the rise of HPV-related throat cancer in men was an excellent argument for vaccinating boys against the virus. And later that month, the CDC extended its vaccine recommendation to include boys as well as girls. But now, researchers say that focusing on vaccinating more members of one sex may be more effective than trying to vaccinate both. In a study published in PLoS Medicine, Johannes A. Bogaards used mathematical modeling to determine which vaccination strategy would lead to the greatest reduction in HPV prevalence. They found that increasing the percentage of girls vaccinated would actually have the biggest effect. Bogaards et al write,

In an important step in the right direction, a CDC panel has recommended that boys as well as girls …
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We show that, once routine vaccination of one sex is in place, increasing the coverage in that sex is much more effective in bolstering herd immunity than switching to a policy that includes both sexes. Universal vaccination against HPV should therefore only become an option when vaccine uptake among girls cannot be further increased. Adding boys to current vaccination programs seems premature, because female coverage rates still leave ample room for improvement in most countries that have introduced HPV vaccination. So far, only three countries have achieved a three-dose coverage of 70% or more in females.

The authors do note that while vaccinating girls and women does offer some protection to men who have sex with men (because some of these men also have sex with women), a supplementary program to vaccinate these men could be a good idea. This might be less than effective in practice — since the vaccine is most effective when given before any HPV exposure, many vaccination programs have targeted children, who may not yet identify with a particular sexual orientation or practice. However, the study authors write that "vaccination of [men who have sex with men] remains cost-effective up to 26 y of age, an age range that might render targeted HPV vaccination acceptable."

Bogaards et al make a persuasive case that, at least if their models are correct, vaccinating all girls would lead to a greater reduction in HPV than vaccinating some girls and some boys. However, they don't address the political obstacles to this plan. As long as HPV is perceived as a women's problem and HPV vaccination as a girls' issue, it will be subject to the hysteria and moralizing that surrounds women's and girls sexuality in the United States. This may prevent the US from ever reaching the level of girls' vaccination that would confer herd immunity. A move to vaccinate boys, however, could increase public support for the project of vaccination in general. Further research needs to look not just at what would reduce HPV prevalence in an ideal world, but at what will work in the sometimes shitty world we actually live in.